The point established by this hadith is that, had offering the prayer over the deceased been an individual obligation, the Messenger of Allah—peace and blessings be upon him—would have offered it himself and would not merely have said, “Pray over your companion.”
As for the merit of the funeral prayer, it is demonstrated by the following report:
Āmir ibn Sa’d ibn Abī Waqqās reported that he was sitting with Abd Allāh ibn Umar when Khabbāb, the owner of the private enclosure, appeared and said, “Abd Allāh ibn Umar! Have you not heard what Abū Hurayrah is saying? He heard the Messenger of Allah—peace and blessings be upon him—say, ‘Whoever accompanies a funeral procession from its home, offers the prayer over it, and then follows it until burial will receive two qīrāts of reward, each qīrāt being equal to Mount Uhud. Whoever offers the prayer over it and then returns will receive a reward equal to Mount Uhud.’”
Ibn Umar then sent Khabbāb to Ā’ishah to ask her about Abū Hurayrah’s statement and return to tell him what she said. Ibn Umar took a handful of pebbles from the mosque and turned them over in his hand until Khabbāb returned. He said, “Ā’ishah said, ‘Abū Hurayrah spoke the truth.’” Ibn Umar struck the ground with the pebbles in his hand and said, “We have indeed missed out on many qīrāts.” Reported by al-Bukhārī and Muslim. (1)
(1) An authentic hadith. It was recorded by al-Bukhārī in several places, including “Book of Funerals,” chapter “One Who Waits Until the Deceased Is Buried,” hadith no. 1325. Muslim also recorded it in “Book of Funerals,” chapter “The Merit of Offering the Funeral Prayer and Following the Procession,” hadith no. 945, and the wording quoted here is his. See *Ahkām al-Janā’iz wa Bida‘uhā* (pp. 67–68).
A useful point: Commenting on the legal implications of the preceding hadith, Ibn Hajar states in *Fath al-Bārī* (3/197): “Its apparent implication is that the qīrāt is reserved for one who is present from the outset until the prayer is completed. Al-Muhibb al-Tabarī and others explicitly stated this. It appears to me, however, that a qīrāt is also earned by one who merely offers the prayer, since everything preceding the prayer is a means of reaching it. Nevertheless, the qīrāt of one who only offers the prayer is less than that of one who, for example, accompanies the procession and also offers the prayer. Muslim’s narration through Abū Sālih, from Abū Hurayrah, states, ‘The smaller of the two is equal to Mount Uhud,’ indicating that the qīrāts vary in magnitude. The same narration of Abū Sālih in Muslim also states, ‘Whoever offers the funeral prayer but does not follow the procession will receive one qīrāt.’ In Ahmad’s narration through Nāfi‘ ibn Jubayr, from Abū Hurayrah, it states, ‘Whoever offers the prayer but does not follow will receive one qīrāt.’ This demonstrates that offering the prayer earns a qīrāt even without following the procession. It is also possible that ‘following’ here refers to following the procession after the prayer.” End quote.